21894991 has 2 divisors, whose sum is σ = 21894992. Its totient is φ = 21894990.

The previous prime is 21894967. The next prime is 21895037. The reversal of 21894991 is 19949812.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21894991 - 2²¹ = 19797839 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21894941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10947495 + 10947496.

It is an arithmetic number, because the mean of its divisors is an integer number (10947496).

Almost surely, 2^21894991 is an apocalyptic number.

21894991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21894991 is an equidigital number, since it uses as much as digits as its factorization.

21894991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 46656, while the sum is 43.

The square root of 21894991 is about 4679.2083732187. The cubic root of 21894991 is about 279.7574046691.

The spelling of 21894991 in words is "twenty-one million, eight hundred ninety-four thousand, nine hundred ninety-one".